Electrical switch



8" 3, 1955 A. B. ANDERSON 2,716,164

ELECTRICAL SWITCH Filed Jan. 21, 1953 //v VEN TOP A. B. ,4 NDERSON WCWWATTORNEV United States Patent ELECTRICAL SWITCH Attell B. Anderson,Bernardsville, N. J., assignor to Bell Telephone Laboratories,Incorporated, New York, N. Y., a corporation of New York ApplicationJanuary 21, 1953, Serial No. 332,290

9 Claims. (Cl. 20027) This invention relates to electrical switches andmore particularly to means for reducing undesired electrostatic voltagesoriginating in the switch mechanism.

In rotary or like switches used in electronic systems for obtainingaccurate samples of a plurality of voltages, spurious voltages whichmodify the samples are obviously objectionable. For example, in a switchof this type known as an automatic zero set switch, and which samplessuccessive voltages from a plurality of circuits and passes the sampleson for controlling the apparatus, a spurious voltage will cause a falsecorrection to be made.

One kind of switch of this type comprises a plurality of equally spacedcantilever-type, contact springs arranged in circular array and adaptedto be successively and momentarily flexed into contact with a commonelectrode. The common electrode comprises a ring mounted in spacedrelation to the array. The flexing of each spring is accomplished bymeans of a rotating arm and roller system. An insulating ring havingguide holes or slots is used to constrain each contact spring to asubstantially radial path. In such a device it has been found thatspurious voltages of electrostatic origin occurred, apparently producedby rubbing of the contact springs on the surfaces of the insulatingguide.

An object of this invention is to reduce spurious voltages in automaticZero set and like switches.

Another object of this invention is to reduce the vibration of acantilever spring-type of contactor.

One feature of this invention resides in a metallic shield or sheath forseparating the movable switch elements of a switching assembly fromtheir insulating guides.

Another feature of the invention involves electrical connection betweenthe movable switch element and its metallic shield or sheath in anassembly of this type.

A further feature of this invention involves a combined shield andswitch element in which the switch element is secured in good mechanicaland electrical connection with the shield.

Other and further objects and features of this invention will appearmore fully and clearly in the following description of illustrativeembodiments of the invention taken in connection with the appendeddrawings in which:

Fig. 1 is a view partly in section, taken on line 1-1 of Fig. 2, of arotary-type switch assembly embodying this invention;

Fig. 2 is a plan view of the switch assembly of Fig. 1;

Fig. 3 is an enlarged longitudinal sectional view of one form ofcombined contactor and shield of this invention;

Fig. 4 is a view of a switch operating roller showing structuraldetails; and

Fig. 5 is a fractional detail view showing a modified form of shield.

As shown in Figs. 1 and 2, the switch assembly comprises a cylindricalhousing in which are secured spaced discs or plates 11 and 12 and ring13 for supporting the various elements of the assembly. The discs orplates 11 and 12 and the ring 13 are advantageously of insulatingmaterial.

A motor 14, mounted centrally of the plates 11 and 12, drives a shaft 15which supports and rotates arms 16. Contact operating rollers 17 arerotatably mounted in forked ends of the arms 16 by conventional means.

The rollers 17 may comprise a bearing 20, advantageously a ball orroller bearing, an insulating body 21 advantageously of non-polardielectric material such as polystyrene, and a metallic shoe or tire 22,as shown in Fig. 4.

Arranged in circular array around the axis of shaft 15, supported byplates 11 and 12 and by ring 13, are a plurality of contactor membersdesignated generally as 23. A common contact ring 24 is secured to oneface of the insulating ring 13 adjacent these contactor members.

The contactor members may each comprise a tubular shield or sheath 25 inone end 26, of which is secured a cantilever spring contactor 27. Theshields or sheaths 25 comprise metallic linings for the orifices insupporting plates 11 and 12 and ring 13. Each shield 25 has a notch orslot 28 for accommodating the rollers 17 and a cutaway portion forming ashoulder 29 fitting around the contact ring 24. The shield illustratedin Figs. 1, 2 and 3 is circular in section, but some other section suchas oval, square, or channel shaped may be used.

The shield or sheath 25a, shown in Fig. 5, is of channel shape havingits opening toward the contact ring 24. Except for having one open side,this sheath is the same as the sheath 25 and the associated elements areall like those in Fig. 3.

In either embodiment, the sheath and the spring contactor advantageouslyare made of the same metal to avoid any possibility of electrolytic orelectrothermal reaction among the'parts.

The cantilever spring contacts 27 are in the path of the rollers 17' andare successively flexed into momentary contact with the contact ring 24as the rollers are rotated'.

The shield 25-, being in close proximity to the spring 27, tends to dampits vibration, thereby inhibiting undesired modes of vibration such asunwanted harmonics. The damping of such vibrations has as one of itspurposes the reduction of fatigue in the spring members and theprolonging of the life of the switch.

Since the metallic linings or sheaths separate the spring contactorsfrom the insulation of the mountings, the possibility of spuriousvoltages due to the rubbing of the springs on the insulation iseliminated by the construction of this invention.

What is claimed is:

1. Switching means comprising an arcuate common contact, a plurality ofcontactors arcuately arranged adjacent thereto, an arcuate insulatorhaving a plurality of metal-lined guide orifices, one for each of saidcontactors, and a rotatable roller for moving each contactorsuccessively into contact with the common contact, the lining andcontactor associated with each orifice being combined and comprising anelongated metal sheath and an elongated metal cantilever spring withinthe sheath and secured thereto at one end only, the sheath includingadjacent the free end of the spring an opening each for the roller andthe common contact.

2. Switching means comprising an arcuate common contact, a plurality ofcontactors arcuately arranged adjacent thereto, an arcuate insulatorhaving a plurality of spaced metal-lined guide orifices, one for each ofsaid contactors, and a rotatable roller for moving each contactorsuccessively into contact with the common contact, the lining andcontactor associated with each orifice being combined and comprising anelongated metal sheath of circular section and an elongated metalcantilever spring within the sheath and secured thereto at one end only,the sheath including adjacent the free end of the spring an opening eachfor the roller and the common contact.

3. Switching means comprising an arcuate common contact, a plurality ofcontactors arcuately arranged adjacent thereto, an arcuate insulatorhaving a plurality of radially extending metal-lined guide slots, onefor each of said contactors, and a rotatable roller for moving eachcontactor successively into contact With the common contact, the liningand contactor associated with each slot being combined and comprising anelongated metal sheath of channel section and an elongated metalcantilever spring within the sheath and secured thereto at one end only,the sheath including adjacent the free end of the spring an opening forthe roller.

4. Switching means comprising an arcuate common contact, a plurality ofcontactors arcuately arranged adjacent thereto, an arcuate insulatorhaving a plurality of metal-lined guide orifices, one for each of saidcontactors, and rotatable means for moving each contactor successivelyinto contact with the common contact, the lining and contactorassociated with each orifice being combined and comprising a metalsheath and a metal spring within the sheath and secured thereto at oneend only, the sheath including adjacent the free end of the spring anopening each for the rotatable means and the common contact.

5. Switching means comprising an arcuate common contact, a plurality ofcontactors arcuately arranged adjacent thereto, an arcuate insulatorhaving a plurality of metal-lined openings, one for each of saidcontactors, and a rotatable roller for moving each contactorsuccessively into contact with the common contact, the lining andcontactor associated with each opening being combined and comprising anelongated sheath and an elongated spring within the sheath and securedthereto at one end only, the clearance between the sheath and the springbeing small to aid in damping vibration of said spring.

6. Switching means comprising a common contact ring, a plurality ofcontactors arranged adjacent to and within said ring, an insulator ringhaving a plurality of metal-lined guide orifices, one for each of saidcontactors, and a rotatable roller for moving each contactorsuccessively into contact with the common contact, the lining andcontactor associated with each orifice being combined and comprising anelongated metal sheath of circular section and an elongated metalcantilever spring coaxial with the sheath and secured thereto at one endonly, the sheath including adjacent the free end of the spring anopening each for the roller and a portion of the common contact ring.

7. Switching means comprising a circular common contact, a plurality ofspaced contactors circularly arranged within the common contact andadjacent thereto, a circular insulator having a plurality of metal-linedguide orifices, one for each of said contactors, and rotatable means formoving each contactor successively into contact with the common contact,the lining and the contactor associated with each orifice being combinedand comprising an elongated cylindrical sheath, an elongated springcoaxial therewith and secured thereto at one end only, the sheathadjacent the free end of the spring having an opening for the rotatablemeans and a notch to accommodate a portion of the common contact.

8. Switching means comprising a circular common contact, a plurality ofspaced contactors circularly ar ranged within the common contact andadjacent thereto, a circular insulator having a plurality of metal-linedguide orifices, one for each of said contactors, and rotatable means formoving each contactor successively into contact with the common contact,the lining and the contactor associated with each orifice being combinedand comprising an elongated cylindrical sheath, an elongated springcoaxial therewith and secured thereto at one end only, the sheath beingclosely adjacent the spring for aiding in damping spring vibration.

9. Switching means comprising a common contact, a plurality of spacedcontactors adjacent the common contact, an insulator having a pluralityof metal-lined guide orifices, one for each of said contactors, andmeans for moving each contactor successively into contact with thecommon contact, the lining and the contactor associated with eachorifice being combined and comprising an elongated sheath, an elongatedspring Within the sheath and secured thereto at one end only.

No references cited.

